ath6kl: Add new state for WOW mode

In addition to existing deep sleep and cut pwr mode, new state
is added in ath6kl_cfg_suspend_mode as well as in ath6kl_state for WOW.

Signed-off-by: Raja Mani <rmani@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>